Journal of Soil and Plant Interactions

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Various species of serpentine leaf miner are serious pests of vegetable crops, especially on cucumber and tomato, in greenhouse and open fields. Reduction of chemical insecticides’ use in order to minimize pesticide residues on these crops is one of the most important aspects of food safety. Yellow sticky cards have been used successfully for many pests and can be used for leaf miners too. Therefore, this investigation was performed to find out how to use these cards, including their height and spacing. To find the most proper height in the first step, three different heights (50, 120 and 170 cm from ground level) were considered, based on randomized complete blocks design with five replications, at the beginning of the growing season (plants with 5-6 leaves and less than 50 cm height). Results showed that traps on 50 cm height captured most of the insects, were in the same statistical group with 120 cm high traps, and had significant difference with 170 cm high treatment. In the second step, at which the experiment was replicated in the peak of adult population, when the plants were in their full height (160 cm), the 170 cm high traps adsorbed most of the adult leaf miners in three days. To find out the best trap spacing, the 170 cm high traps were placed at three different spacing of 1, 2 and 3 m and were compared to control (no trap). Results revealed that 1 m spacing treatment had the best efficiency, was in the same group with 2 m spacing treatment, and had significant difference with other treatments.

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Extensive use of chemical pesticides to control pests in developed and developing countries has led to the increase in crop production and decrease in post-harvest losses, which has caused harmful effects on human health. When the amount of pesticides exceeds permissible limits, some measures should be undertaken to reduce their application. In order to control cucumber pests in greenhouse, farmers use pesticides extensively, which their residues threaten human health in the society. Due to the importance of this problem, the residue and pre-harvest period of the Imidacloprid insecticide in some of the greenhouses of Varamin region, Tehran province, Iran was measured. In order to determine the pre-harvest period, spraying of Imidacloprid pesticide was done in a completely randomized block design with three replications, and two treatments of Imidacloprid and control (no insecticide). Sampling was done 1, 2, 3, 5, 7, 10 and 14 days after spraying. Samples were then transferred to the laboratory and preserved in freezer until the extraction and purification were performed and the amount of pesticide residues was measured. Based on the results, Imidacloprid residue reached below the maximum residue level (MRL) of 1 mg/kg two days after spraying. But for more confidence, the third day after spraying was considered as the pre-harvest period. Sampling for determination of Imidacloprid residue was performed in four greenhouses of Varamin region. The results showed that mean Imidacloprid residue levels were above the MRL value in these greenhouses.

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Considering the increase of using vermicompost fertilizers in greenhouse cultivation, effect of vermicompost application on growth characteristics of tomato and one of its major pests [greenhouse whitefly, Trialeurodes vaporariorum (Hem:Aleyrodidae)] was investigated. The experiment consisted of five treatments: control (without vermicompost), 30% and 60% solid vermicompost fertilizer, and 40% and 20% aqueous extracts of vermicompost. Effect of vermicompost on greenhouse whitefly was tested for two different cases of with-choice and no-choice. Results showed that significant increase in shoot dry weight and root dry weight of tomato in vermicompost treatments. The highest increase (18 and 12 fold, respectively) was observed in plants treated with 60% solid vermicompost. The highest amount of nitrogen (0.43 mg/kg), potassium (14.56 mg/kg) and phenol (1130.46 ppm) was recorded in60% solid vermicompost treatment. Also, application of vermicompost reduced the percentage of infested leaves to whitefly, such that the lowest amounts were 6.67% and 8.97% in 60% and 30% solid vermicompost treatments, respectively, and 10.53% in 40% aqueous extract of vermicompost. The mortality of the second instar nymph of greenhouse whitefly-the stage that insects become fixed to the leaves by their sucking mouthparts- was increased (about 10%) by application of  vermicompost.

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Aphis gossypii Glover (Hem.: Aphididae) is an important pest of vegetables and ornamental plants in greenhouses. Continued use of chemical pesticides for control of this pest has caused several problems and it is necessary to use other management methods, such as biological control. Coccinula elegantula weise (Col.: Coccinellidae) is one the natural enemies of cotton aphid with effective role in control of this pest. In this study, the effect of temperature was investigated on functional response and predation potential of this coccinellid with respect to different densities of the aphid. Based on the results, the predator exhibited type II functional response at three tested temperatures (18, 25 and 32 °C). By increasing the temperature from 18 to 25 °C, handling time of C. elegantula was significantly increased and searching efficiency was decreased; but these parameters didn’t change when the temperature increased from 25 to 32 °C. According to the results of the present study, in which the high searching rate and short handling time of C. elegantula were found to be at 25 and 32 °C and the fact that optimum temperature range for A. gossypii development over cucumber is 22.5 to 30 °C, and more importantly if we can overcome the obstacles of mass rearing, this predator could be a valuable and potential species in biological control of cotton aphid

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In an experiment the effective dose and the time of application of phenamiphos (Nemacur 10G) for control of the root knot nematode, Meloidogyne javanica, infecting cucumber, was found out to be 22.5 g/m2 of commercial product and the best time of its application was one week prior to sowing of seeds. However, the results revealed that in concomitant and sequential (one week before) treatment, highest yield were obtained. For the determination of Nemacur residue of the most effective dose of 22.5 gr/m2 the products of the treatment blocks were harvested for six times. The samples were transferred to the laboratory and then prepared for extraction, purification and finally measurement of the residues by GC-NPD. The results were compared with the Codex Alimentarius MRL for Nemacur on a vegetable which is 0.5 ppm and the best timing for pesticide application which was estimated to be one week before sowing of seeds was chosen. It is therefore suggested that the cucumbers produced up to 4th stage of harvesting be used by the consumers, because the products harvested up to this stage possess residues which are closed to the MRL shown by codex Alimentarius.

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Chrysanthemum aphid (Macrosiphoniella sanborni) is one of the most important pests of chrysanthemum (Chrysanthemum morifolium); while there is little information about the interaction of chrysanthemum and chrysanthemum aphid. In the present study, interaction of different chrysanthemum cultivars and aphid populations was assessed through evaluation of morpho-physiological traits. For this purpose, 14 chrysanthemum cultivars were cultivated in a greenhouse at Isfahan University of Technology, Isfahan, Iran, using a factorial experiment in a completely randomized design with three replications. According to the results of analysis of variance, presence of aphid significantly affected all measured plant’s growth parameters. The studied traits showed negative responses to stress conditions. The highest reduction effect was related to photosynthesis. Also, the respiration rate was increased in relation to photosynthesis among the infected plants. In addition, presence of the pest reduced the proportion of open buds to total buds on the plant, decreased plant height and delayed flowering period among the infected plants. Although the growth of aphid population in different cultivars was not exactly the same during different days, but the trend was relatively similar. Despite the relatively high number of aphids on the flowers of “Ordibehesht” cultivar, they still had good quality. Overall, based on the results of this study, aphids can significantly affect the chrysanthemum plant's vegetative and reproductive growth